Process and means for preventing film deposits in lamps



March 30, 1954 s. c. SLIFKIN 2,673,940

PROCESS AND MEANS FOR PREVENTING FILM DEPOSITS IN LAMPS Filed April 28,1951 DISTILLED WATER v INVENTOR SAM. CHARLES SL/FKIN Ma W ATTORNEYSPatented Mar. 30, 1954 PROCESS AND MEANS FOR PREVENTING FILM DEPOSITS INLAMPS Sam 0. Slifkin, Melrose Park, IlL, assignor to General Aniline &Film'Corporation, New York, N. Y., a corporation of Delaware ApplicationApril 28, 1951, Serial No. 223,551

This invention relates to cooling high intensity gaseous dischargelamps, and more particularly to an arrangement for cooling mercury vaporcapillary arc lamps.

High intensity light sources of the type known as mercury vaporcapillary arc lamps develop an intense heat which, if not absorbed bycooling, will-destroy the lamp. Therefore, it is necessary to cool theselamps either by an air blast, or, preferably, by flow of cooling liquid.To this end, the lamp is enclosed in a transparent jacket through whichthe cooling liquid, in intimate contact with the lamp surface, ispassed.

Capillary arc lamps are only a few inches in size, but develop close to200,000 candle power per square inch (approaching the brightness of highintensity carbon arcs). The physical construction necessitates largeelectrodes in propor. tion to the overall size of the lamp. Theseelectrodes cannot be isolated from the cooling system, but must beimmersed in the cooling liquid to be also cooled thereby. Ihe terminalvoltage between electrodes is high, approximately 1200 volts at thestart, and, under normal operation, between 800 to 900 volts.

In open flow-cooling systems, where a continuous supply of Wellor citywater is available, it has been observed that adarlz deposit is formedupon the outer wall of the lamp and on the inner wall of the jacket.This deposit forms a film which not only strongly absorbs the 'actiniclight radiated from the lamp and thereby impairs the chic'iency, butalso shortens its life, since the cooling becomes less effective,resulting in a temperature increase beyond the safe limit which rapidlydestroys the lamp. Moreover, when metallic ions collect on the outerwa'llof the lamp, a current conductive path-ofrelatively low resistanceis produced in shunt With the terminal electrodes. The localized heatingeffect of the current flowing in the shunt path will crack .theglassenvelope of the lamp. This film forms after a fewhours of operation,andcan onlybe-removed bycleaning of the lamp assembly. This deposit .isattributed to dissolved impurities in the water, and subsequentoxidation of metallic ions.

In a closed circuit cooling system, where the water from a storage tankis recirculated through the jacket of the tube, distilled water, freefrom impurities, proves no more effective in eliminating theabove-mentioned disadvantages. Formation of a light-absorbing deposit ata fairly rapid rate is not eliminated by the use of distilled water, sothat frequent disassembly and cleaning of the tube and the jacket arerequired. Chemical 2 Claims. (Cl. 313-423) 2 inhibitors have been tried,such as trisodium phosphate, with little benefit except that it sloweddown the formation of deposit extending the effective use of the lamp toa period of a few hours longer.

It is a primary object of this invention to prevent, substantiallycompletely, the formation of light-absorbing deposits inwater cooledmercury arc lamps, and to this end means are provided, in.

a closed circulatory cooling system, to restrain a build-up of metallicions.

A particular feature of this invention is that by inclusion in thecooling system of simple apparatus, the above-mentioned disadvantagesare entirely eliminated resulting in a continuous and substantiallyindefinite operation of such lamps, limited only by their normal lifeperiod.

Other objects and features will be apparent from the followingdescription of the invention, pointed out in particularity in theappended claims and taken in connection with the accompanying drawings,in which:

Figure 1 is a schematic representation of the closed circulatory coolingsystem;

Figure 2 is a perspective view of the capillary arc lamp placed in thejacket; and

Figure 3 is an enlarged cross-sectional view of the container which is acomponent element of the cooling system shown in Figure l.

Referring to the figures, the mercury arc lamp 6 is of tubularconstruction having terminal electrodes l and 7 A transparent jacket 8surrounds the lamp 6 forming a cylindrical housing with suitable metalfittings l0 and ID at each end, having fittings H and H to whichsuitable pipe or hose connections may be made. The jacket 8 has an innertubular portion 12 of narrower diameter which will be described ingreater detail in connection with Figure '2.

The cooling system consists essentially of the cooling liquid storagetank I 4, the pump 1 5 driven by a suitable motor Mfor propelling theliquid at a given rate of flow, a container l6 through which the liquidmust pass which is the essential element in applying the invention, andpipes l1 interconnecting these components into a closed recirculatingsystem.

Only as much of the component elements of the cooling system are shownhere, for the sake of simplicity, which are necessary for theunderstanding of the application and operation of the invention. Suchsystems generally also include some form of a heat exchanger, variousvalves, thermostatic controls, and safety interlock switches.

The construction of the jacket 8 can better be seen in the perspectiveview of Figure 2, where similar reference characters denote identicalcomponent elements. The cylindrical jacket 8 has an inwardly extendinginner tube portion at one end thereof which forms a velocity tube aroundthe lamp 6, constraining the cooling liquid to flow past the lamp 6 atincreased velocity, due to the restriction of the cross-section of thewater passage.

The cross-sectional view of Figure 3 indicates that the container H isfilled with a chemical composition for the purpose described below.

The closed circulating cooling system, shown in Figure 1, represents, byway of example, a simple arrangement whereby distilled water placed inthe storage tank 14 may be recirculated by means of the pump 15 andforced to flow through the cOoling jacket 8 and through the containerHi. In view of the fact that the electrodes 1 and 1 are immersed in thecooling water, and one of these terminals is generally placed at groundpotential, it is necessary to insulate the other terminal from theconductive portions of the system. For this purpose, a flexible hose l9,preferably of rubber or other suitable electrical insulating material,is inserted into the metal conduit at one point of the system. Theterminals of the lamp 6 may be brought out through the fittings lli andIll. Since this invention is not concerned with the electrical portionof the system, the electrical connection to the lamp is merely indicatedby leads :0 and between which the electrical potential applied is shownby a con ventional sign for alternating current.

It was mentioned before that the use of distilled water, free fromimpurities, has not lessened the formation of a light absorbing depositon the lamp 6 or on the inner wall of the jacket 8, and, particularly,on the velocity tube I2. That this deposit formation was due toelectrolysis of the metal electrodes, when ordinary water of even verylow conductivity was used, has been recognized, and chemical inhibitorsadvocated for repressing the formation of simple metallic ions. Withpure, distilled water as the cooling liquid, the discoloration of thewater and the formation of deposit has been a puzzling phenomenon, andonly temporary remedy effected by the use of such inhibitors. Trisodiumphosphate in any concentration did not prevent the oxidation of ferrousor manganous ions, permitting more of the phosphate-complexed ions todissociate and be deposited on the lamp and jacket.

I have considered this, and come to the conclusion that although puredistilled water is used, which has an extremely high specificresistance, as soon as a potential difference exists between theelectrodes, a few free ions present will produce an infinitesimalcurrent conductivity which will bring additional metal ions intosolution. These ions in turn produce a greater increase of current andelectrolysis becomes more rapid. This reaction is, in effect,autocatalytic, since once electrolysis has started, the solutiondeteriorates at an ever increasing rate. Another possible source ofsoluble metallic ions is from the gal- Number vanic effects produced inthe system because of the presence of impure and of dissimilar electrodemetals producing electrolytic couples or miniature batteries. Smallelectric current leakages will, of course, enhance such effects.

To overcome this undesired reaction, in accordance with this invention,an ion exchange medium is placed in the circulating system. This ionexchanger medium is held in the container 16 and may comprise a cationicexchange resin consisting of polynaphthalene sulfonic acid formaldehydederivatives. It is preferred to include also an anionic exchange resin,for example, a resinous condensation product of urea ethylenediamine andformaldehyde. Therefore, this resin bed is made up of the mixture ofcation and anion active resins, and all ions, whether metallic ornonmetallic, are captured as the given portion of the water passesthrough the bed. Consequently,

there is never an opportunity for the ion concentration to risesufficiently to support electrolysis.

Resins of the type mentioned are readily available and are being used aswater softeners in the industry. In their above-described use, inconnection with distilled water, they perform a different function,namely to prevent electrolysis by retaining any free ions. Just as theformation of ions producing electrolysis is normally autocatalytic inrate, the action of the anionic and cationic exchange resin bed is anegative counterpart in that the capture of free ions progressivelydecreases, resulting in a state of complete deionization, which is thenmaintained substantially indefinitely. For this reason, in practice,such resin beds need be replaced very infrequently, if at all.

This is in part a continuation of my copending application Serial No.695,333, filed September 6, 1946, now abandoned.

I claim:

1. The combination with a water-cooled electric lamp wherein the lamp ismounted between electric-supply terminals, in a jacket in a systemthrough which the cooling water circulates in contact with saidterminals, of ion-exchange means comprising a mixture of anion andcation exchange resins for treating said water during the circulationthereof in said system to prevent the deposition of a coating on theexterior of said lamp.

2. A process of minimizing the formation of a coating on the quartz tubeof a water-cooled electric lamp in which cooling water is circulatedthrough the lamp to cool the quartz tube thereof and in which the lampterminals are immersed in the cooling water, which process comprisespass ing the circulating stream of cooling water through a bed composedof a mixture of anion and cation exchange resins.

SAM C. SLIFKIN.

UNITED STATES PATENTS Name Date 2,245,406 Lemmens June 10. 1941

1. THE COMBINATION WITH A WATER-COOLED ELECTRIC LAMP WHEREIN THE LAMP ISMOUNTED BETWEEN ELECTRIC-SUPPLY TERMINALS, IN A JACKET IN A SYSTEMTHROUGH WHICH THE COOLING WATER CIRCULATES IN CONTACT WITH SAIDTERMINALS, OF ION-EXCHANGE MEANS COMPRISING A MIXTURE OF ANION ANDCATION EXCHANGE RESINS FOR TREATING SAID WATER DURING THE CIRCULATIONTHEREOF IN SAID SYSTEM TO PREVENT THE DEPOSITION OF A COATING ON THEECTERIOR OF SAID LAMP.